Device and method for registering a position sensor in an anatomical body

ABSTRACT

An apparatus having an insertable portion for holding a position sensor is disclosed. The position sensor can transmit a signal indicative of its position with respect to a field generator. The insertable portion of the catheter has fiducial markings that are detectable by an imaging modality when the insertable portion is inserted into the anatomical body. The fiducial markings are asymmetrical about at least a first axis of the insertable portion. After the insertable portion has been inserted into the anatomical body, the fiducial markings can be detected to facilitate registration of the position sensor held in the insertable portion to the anatomical body. The apparatus also has a fixing mechanism for releasably fixing the insertable portion to the anatomical body. The non-symmetrical fiducial markings facilitate unambiguous registration of the insertable portion to the anatomical body. When the insertable portion is inserted into the anatomical body to a location of interest, the fixing mechanism substantially rigidly fixes the insertable portion of the catheter to a part of the anatomical body near the location of interest.

RELATED INVENTION

This application is a continuation-in-part of U.S. application Ser. No.10/067,993, now U.S. Pat. No. 6,785,571, entitled “Device and Method forRegistering a Position Sensor in an Anatomical Body” which is acontinuation-in-part application of U.S. application Ser. No.09/820,796, now abandoned, filed Mar. 30, 2001 and entitled “Device andMethod for Registering a Position Sensor in an Anatomical Body”.

FIELD OF THE INVENTION

This invention relates to devices and methods to insert position sensorsinto an anatomical body. More particularly, the present inventionrelates to a device and method for registering a position sensorinserted in an anatomical body.

BACKGROUND OF THE INVENTION

Position sensors have been increasing in accuracy and decreasing insize. This has made position sensors for use in tracking portions of ananatomical body during surgical procedures more feasible.

However, in order to accurately track areas of interest in an anatomicalbody, it is necessary to rigidly fix the position sensor near or at alocation of interest in the anatomical body. It is also necessary tothen register the position sensor with the anatomical body. A positionsensor is registered to an anatomical body by correlating the positionof the position sensor in the anatomical body to the determined positionof the position sensor in the frame of reference. At that time, thelocation of interest in the anatomical body can be tracked in a fixedframe of reference, such as the operating room frame of reference, bydetermining the position of the position sensor.

A number of position sensors have been used in the past. Recently,magnetic sensor coils or fibre optic sensors that are reasonably small,and therefore can be substantially unobtrusively inserted into ananatomical body, have been successfully used.

However, the prior art suffers from the disadvantage that it isdifficult to register the position sensors to the anatomical body.Methods for registering the position sensor in the anatomical body haveincluded obtaining an image of the anatomical body after insertion ofthe position sensor and attempting to register the position sensor tothe anatomical body from the acquired image. However, this suffers fromthe disadvantage that the position sensor is not always easilyidentifiable in the acquired image. Furthermore, while it may bepossible to determine the position of the position sensor in theanatomical body, sufficient information may not be available from theimage to determine and register both the position as well as orientationof the position sensor. Because of this, it may not be possible todetermine all of the degrees of freedom, such as movement along the x,y, z axes, as well as three orientation coordinates, namely pitch, yawand roll.

In some embodiments, it may be desirable that the position sensor bepermitted to move relative to the anatomical body. However, in mostcases, it is preferred that there be no relative movement between theposition sensor and the location of interest in the anatomical body.Most prior art devices and methods for registering the position sensorin an anatomical body suffer from the disadvantage that there may berelative movement between the position sensor and the anatomical body.Accordingly, in addition to a method and device for accuratelyregistering the position of the position sensor in an anatomical body,there is a need in the art for a device and method to reliably fix theposition sensor to the anatomical body, thereby avoiding relativemovement during the procedure. There is also a need in the art forreliable devices and methods to insert the position sensor into theanatomical body.

SUMMARY OF THE INVENTION

Accordingly, it is an object of this invention to at least partiallyovercome the disadvantages of the prior art. Also, it is an object ofthis invention to provide an improved type of device and method thatfacilitates simple and accurate registration of a position sensor withinan anatomical body. It is also an object of this invention to provide animproved type of device and method to minimize relative movement betweenthe position sensor and the anatomical body.

Accordingly, in one of its aspects, this invention resides in anapparatus insertable into an anatomical body, said apparatus comprising:an insertable portion for holding a position sensor that can transmit asignal indicative of its position in a frame of reference; fiducialmarkings on the insertable portion, said fiducial markings beingdetectable by an imaging modality when the insertable portion isinserted in the anatomical body and permitting the position andorientation of the insertable portion to be determined, said insertableportion substantially rigidly holding the position sensor at a knownspatial position with respect to the fiducial markings; wherein thefiducial markings are non-symmetrical about at least a first axis of theinsertable portion; wherein, after insertion in the anatomical body, thefiducial markings can be detected by the imaging modality to facilitateunambiguous registration to the anatomical body of the position sensorrigidly held in the insertable portion by correlating the fiducialmarkings detected by the imaging modality to the determined position ofthe position sensor in the frame of reference.

In a further aspect, the present invention resides a method ofregistering a position sensor to an anatomical body, said methodcomprising the steps of: (a) fixing a position sensor to an insertableportion of an apparatus, said insertable portion having fiducialmarkings thereon; (b) inserting the insertable portion of the apparatusto a location of interest in the anatomical body; and (c)detecting thenon-symmetrical fiducial markings on the insertable portion of theapparatus to facilitate registration of the position sensor in theinsertable portion to the anatomical body by: (c1) detecting thefiducial markings on the insertable portion; (c2)determining theposition of the position sensor in a frame of reference; and (c3)registering the position sensor to the anatomical body by correlatingthe detected fiducial markings to the determined position of theposition sensor in the frame of reference.

In a further aspect, the present invention resides a device forfacilitating tracking of an apparatus in an anatomical body, said devicecomprising: an insertable portion for holding a position sensor that cantransmit a position signal indicative of its position in a frame ofreference; non-symmetrical fiducial markings on the insertable portion,said non-symmetrical fiducial markings being detectable by an imagingmodality to facilitate unambiguous registration of the position sensorheld in the insertable portion to the anatomical body; wherein theapparatus can insert the insertable portion into the anatomical body,and, the position signal transmitted from the position sensor indicatesthe position of the apparatus near the position sensor; wherein theinsertable portion substantially rigidly holds the sensor at a knownspatial position with respect to the fiducial markings; and wherein,after insertion of the insertable portion in the anatomical body, animage of the insertable portion can be obtained by the imaging modality,and, the position sensor can be registered to the anatomical body bycorrelating the fiducial markings detected by the imaging modality tothe determined position of the position sensor in the frame ofreference.

In one preferred embodiment, the present invention comprises fiducialmarkings which are not symmetrical along at least one axis. In otherwords, the fiducial markings are arranged such that the position,orientation and direction of pointing of the fiducial markings can bedetermined from the image of the fiducial markings detected by theimaging modality. This facilitates unambiguous registration by avoidingthe possibility that the orientation and/or direction of the positionsensor in the anatomical body is misinterpreted from the detected imageof the fiducial markings.

In one aspect, the apparatus comprises a fixing mechanism for releasablyfixing the insertable portion of the apparatus to the anatomical body ata location of interest. The fixing mechanism can be any type ofmechanism that can releasably and rigidly fix the insertable portion tothe anatomical body, such that the insertable portion will not becomeeasily displaced during the procedure. In one embodiment, the fixingmechanism comprises a screw that screws into a part of the anatomicalbody, or, at least one barb that can become fixed to the anatomical bodynear the location of interest.

The fixing mechanism may also comprise an inflatable member thatinflates when the insertable portion is at the location of interest.More preferably, the inflatable member has lobes that can inflate to fixthe catheter, such as in a passageway near the location of interest,while still permitting fluid flow around the apparatus, such as acatheter, and through the passageway.

In a further preferred embodiment, the fixing mechanism comprises aplurality of movable fingers having gripping elements. The movablefingers have a collapsed configuration where the gripping elements arenear the apparatus, such as a catheter or a needle, and permit insertionof the catheter into the anatomical body and near the location ofinterest. The movable fingers also have a deployed configuration wherethe gripping elements engage a surface of a passageway in the anatomicalbody to fix the insertable portion to the anatomical body near thelocation of interest, but permit fluid flow around the apparatus andthrough the passageway.

One advantage of the present invention is that the fiducial markings onthe insertable portion permit the position, and preferably orientation,of the insertable portion to be accurately determined with respect tothe anatomical body. As the position of the position sensor with respectto the insertable portion, and therefore the fiducial markings, isknown, the position sensor can then be registered to the anatomical bodyby correlating the position of the fiducial markings in the images tothe determined position of the position sensor in the fixed frame ofreference.

A further advantage of the present invention is that the fixingmechanism preferably substantially rigidly fixes the insertable portionof the apparatus to the anatomical body. In this way, once the positionsensor has been registered, relative movement between the anatomicalbody and the position sensor is decreased.

Further aspects of the invention will become apparent upon reading thefollowing detailed description and drawings that illustrate theinvention and preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate embodiments of the invention:

FIG. 1A is a symbolic representation of a position sensor system asknown in the art.

FIG. 1B is an illustration of a position sensor system as known in theart.

FIG. 2A illustrates an apparatus comprising a catheter having aninflatable member according to one embodiment of the present invention.

FIG. 2B is an enlarged detailed drawing of the guidewire and cathetershown in FIG. 2A.

FIG. 2C is a detailed drawing of a catheter having an inflatable memberaccording to a further embodiment of the present invention.

FIG. 2D is a drawing of the catheter shown in FIG. 2C with theinflatable member inflated.

FIG. 3A is a front section view of a catheter having an inflatablemember according to a further embodiment of the present invention.

FIG. 3B is a side section view of the catheter shown in FIG. 3A.

FIG. 3C is a side view of an alternate embodiment of the inflatablemember shown in FIG. 3B.

FIG. 4A is a side view of a catheter in a deployed configurationaccording to a further embodiment of the present invention.

FIG. 4B is a side view of the catheter shown in FIG. 4A in a collapsedconfiguration.

FIG. 5 shows a side view of the rigid portion of the catheter accordingto a further embodiment of the present invention.

FIG. 6A shows a detailed view of the catheter according to a furtherembodiment of the present invention.

FIG. 6B shows a side view of the catheter shown in FIG. 6A attached to acannulated screwdriver.

FIG. 7 illustrates an insertable portion in the form of a styletteinsertable in a needle, according to a further embodiment of the presentinvention.

FIGS. 8 a and 8 b illustrates an apparatus comprising a needle and aninsertable portion in the form of a stylette releasably fixed into theneedle according to a further embodiment of the present invention.

FIG. 8 c illustrates the needle shown in FIGS. 8 a and 8 b, but with theinsertable portion removed.

FIG. 9 illustrates an apparatus according to one embodiment of theinvention having a needle, a stylette and the insertable portion in theform of a secondary stylette.

FIG. 10 illustrates a needle with therapy or sensor zones according to afurther embodiment of the present invention.

FIG. 11 illustrates an embodiment of the present invention having twoposition sensors longitudinally displaced according to a furtherembodiment of the present invention.

FIG. 12 illustrates an insertable portion for insertion in a needle withthe insertable portion having a fixing mechanism.

FIGS. 13 a, 13 b and 13 c illustrate the deployment of the fixingmechanisms shown in FIG. 12.

FIGS. 14 a, 14 b, 14 c and 14 d illustrate the process by which theposition sensor is registered using an insertable portion havingfiducial markings which are not symmetrical along at least one axisaccording to one embodiment of the present invention.

FIGS. 15 a and 15 b illustrate a side view and perspective view,respectively, of an insertable portion having fiducial markings whichare not symmetrical about at least one axis, according to a preferredembodiment of the present invention.

FIGS. 16 a and 16 b are representations of a side view and a perspectiveview of the detected fiducial markings for the insertable portionillustrated in FIGS. 15 a and 15 b.

FIGS. 17 a, 17 b and 17 c illustrate an insertable rigid portioncomprising a mantle and a sensor rigidly attached thereto with themantle being asymmetric along at least one axis according to oneembodiment of the present invention.

FIGS. 18 a, 18 b and 18 c illustrate an insertable rigid portioncomprising a mantle and a sensor rigidly attached thereto with themantle being symmetric upon all three axes.

FIGS. 19 a and 19 b illustrate a side view and a perspective view of amantle being asymmetric along all three axes such that no axis or planeof symmetry exists according to a further embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1A and 1B show a conventional position sensor system, showngenerally by reference numeral 10. The system 10 comprises a controlunit 12 that is connected to a field generator 14 and a host computer16. The host computer 16 can be a user supplied work station. The fieldgenerator 14 generates a complex electromagnetic field within a frame ofreference. A position sensor 20 within the frame of reference can sensethe complex electromagnetic field. The system 10 also comprises a sensorinterface unit 18 that interfaces the control unit 12 to the positionsensor 20. It is understood that these components may be integratedtogether. For example, the sensor interface unit 18 may be combined withthe control unit 12.

The position sensor 20 generally comprises a sensor element, such as amagnetic sensor coil 21, which reacts to, or senses, the complexelectromagnetic field generated by the field generator 14. As theposition sensor 20 moves in the electromagnetic field generated by thefield generator 14, the sensor coil 21 generates a position signal S_(P)that is indicative of the position of the position sensor 20. Generally,the sensor coil 21 will react to changes to both the position andorientation of the position sensor 20 in the frame of reference. In thisway, the position signals S_(P) generated by the sensor coil 21 areindicative of both position and orientation of the position sensor 20.The position signals S_(P) are received by the sensor interface unit 18and converted to a form which can be understood by the host computer 16.

Thus, the position and orientation of the position sensor 20 can bedetermined in the frame of reference of the field generator 14. Theframe of reference of the field generator 14 is generally a fixed frameof reference, such as the frame of reference of the operating room.

In order for the position sensor 20 to be of assistance in tracking ordetermining the position and orientation of a location of interest in ananatomical body, it is necessary that the position sensor 20 beregistered with respect to the location of interest in the anatomicalbody. In addition, it is often desirable that the position sensor 20 isfixed in some way to the anatomical body so that, once the positionsensor 20 is registered to the anatomical body, the position sensor 20will not move with respect to the anatomical body.

FIGS. 2A, 2B, 2C and 2D show an apparatus, shown generally in FIG. 2A byreference numeral 100, to facilitate inserting, fixing and registering aposition sensor 20 into the anatomical body according to one embodimentof the present invention. The apparatus 100 in this embodiment comprisesthe sensor coil 21 held within an insertable portion 90. In thisembodiment, the apparatus 100 comprises a catheter 110 for inserting theinsertable portion 90 into the anatomical body. The catheter 110 movesalong a guidewire 60, as is known in the art. The catheter 110 will moveinto a passageway of the anatomical body until the position sensor 20 isnear a location of interest in the anatomical body. The location ofinterest is the part of the anatomical body whose position is desired tobe determined and tracked during a procedure.

In this embodiment, the apparatus 100 also comprises electrical leads 26which extend from the position sensor 20, and in particular, the sensorcoil 21, outwards through a plug connector 24, shown in FIG. 2A. Theelectrical leads 26 transmit the position signals S_(P) from the sensorcoil 21 of the position sensor 20 to the sensor interface unit 18, thecontrol unit 12, and to the host computer 16. The plug connector 24connects to the sensor interface unit 18 of the system 10.

The apparatus 100 also comprises a fixing mechanism, shown generally byreference numeral 28. In the embodiment shown in FIG. 2B, the fixingmechanism 28 comprises an inflatable member 30, such as a balloon, whichexpands radially outwards from the longitudinal axis of the insertableportion 90 when inflated. The catheter 110 also comprises an inflatableopening 44 that is used in this embodiment for providing air, or otherfluid, to the inflatable member 30. It is understood that if a differenttype of fixing mechanism 28, other than an inflatable member 30, isused, an inflatable opening 44 may not be required or may be substitutedwith an alternate activation pathway or method. The catheter 110 alsocomprises a guide path opening 40, as is known in the art.

In operation, the catheter 110 is inserted into the anatomical body byplacing the catheter 110 over the guidewire 60 at the distal end, as isknown in the art. The insertable portion 90 of the catheter 110 willthen be lead to a passageway near the location of interest in theanatomical body. In the preferred embodiment, once the insertableportion 90 is near the location of interest, the inflatable member 30will be inflated by passing air through the inflatable opening 44. Theinflatable member 30 will then expand radially to the sides of thepassageway, thereby rigidly fixing the insertable portion 90 to thepassageway near the location of interest.

Once the insertable portion 90 is fixed to a part of the anatomical bodynear the location of interest, an image of the location of interest canbe made using a known imaging modality. It is noted that the insertableportion 90 has fiducial markings 70 which are detectable by the imagingmodality after insertion of the insertable portion 90 into theanatomical body. Detection of the fiducial markings 70 by the imagingmodality facilitates registration of the position sensor 20 to theanatomical body.

Preferably, the position sensor 20 is held in the insertable portion 90so that the distance and orientation of the position sensor 20 withrespect to the fiducial markings 70 will remain constant. To accomplishthis, it is generally preferred that the insertable portion 90 is rigidor substantially rigid so that the distance and orientation of theposition sensor 20 with respect to the fiducial markings 70 will remainsubstantially constant. In general, the insertable portion 90 should beas rigid as required by the particular position sensor 20 being used.For instance, if the position sensor 20 can detect movement, such asbending, then the insertable portion 90 can be less rigid, provided theposition sensor 20 could compensate for this lack of rigidity by sensingthis bending movement. In a preferred embodiment, the insertable portion90 is substantially rigid so as to maintain the position and orientationof the fiducial markings 70 with respect to the insertable portion 90substantially constant.

In a preferred embodiment, the imaging modality can comprise CT scans,fluoroscopic images and ultrasound images. When the imaging modalitycomprises CT scans and fluoroscopic images, the fiducial markings 70preferably comprise a radio-opaque substance. The fiducial markings 70,as well as the insertable portion 90 and the catheter 110, should alsobe made from a substance that does not react with anatomical bodies.Preferably, when the imaging modality comprises CT scans andfluoroscopy, it is preferred that the fiducial markings 70 comprisetantalum.

During the procedure, the fiducial markings 70 can perform a dualpurpose. Firstly, the fiducial markings assist in guiding the catheter110 to an anatomical body near the area of interest when viewed with afluoroscope, for example. Secondly, the fiducial markings 70 facilitateregistration by quantitatively co-locating the position sensor 20 in theimage with the detected position of the position sensor 20 in the frameof reference. In other words, by determining the location of thefiducial markings 70 in the image, and knowing the distance andorientation of the fiducial markings 70 with respect to the positionsensor 20 which is rigidly held in the insertable portion 90 of thecatheter 110, an automatic registration can be made between thedetermined position of the position sensor 20 using the position sensorsystem 10 and the determined position of the position sensor 20 usingthe fiducial markings 70 in the image. The fiducial markings 70 detectedby the imaging modality can be used to determine the position andorientation of the position sensor 20 in the image, and therefore theanatomical body. As stated above, the insertable portion 90 ispreferably rigid or semi-rigid, as required to determine the positionand orientation of the position sensor 20 from the fiducial markings 70.

In order to facilitate registration, it is preferred that the fiducialmarkings 70 comprise at least two markings 71, 72 which permit theposition and orientation of the insertable portion 90 to be determinedin the image. As shown in FIG. 2B, the at least two markings 71, 72 arebands around the insertable portion 90. Furthermore, in order toincrease the accuracy, it is preferred that the at least two markings71, 72 be located at opposed ends of the insertable portion 90, andpreferably as far apart as possible, while remaining on the insertableportion 90. To assist in registering the position sensor 20, the shadowof the position sensor 20, such as the sensor coil 21 in thisembodiment, can be used as a further marker in the image obtained by theimaging modality.

As shown in FIG. 2B, the at least two markings 71, 72 are bands whichextend around the circumference of the insertable portion 90. Inaddition, the fiducial markings 70 may comprise a bead 73 as shown inFIG. 2C. A band 74 would preferably still be used in association withthe bead 73 as the band 74 can be used to more easily identify theorientation of the insertable portion 90. In addition, the fiducialmarkings 70 may comprise a series (not shown) of beads 73, which canalso be used to identify the orientation. Also, a series of bands 74 maybe used to increase accuracy.

The fiducial markings 70 should have any position, orientation or shapethat permits determination of the position and orientation of theposition sensor 20 held by the insertable portion 90 by the imagingmodality. While a number of fiducial markings 70 may be used in theinsertable portion 90, at least two markings 71, 72 will generally berequired to determine both the position and orientation of theinsertable portion 90. If, in a particular situation, only the positionand not the orientation need be determined, one fiducial marking 70 maybe used. Furthermore, in some cases, the sensor element in the positionsensor 20 may not be able to determine six degrees of movement. Forinstance, when the sensor element is a magnetic sensor element 21, asshown in FIGS. 2A, 2B, 2C and 2D, it may be difficult to determine rollusing the system 10. In this case, if the position sensor 20 cannotdetermine roll, it is not necessary to use the fiducial markings 70which can identify the roll orientation of the position sensor 20.Accordingly, the fiducial markings 70 may only be required to identifysome of the six degrees of freedom, and may not be required for allthree positions or all three orientations, depending on the particularsituation. Furthermore, the fiducial markings 70 need not be twoseparate markings, but rather may be a single complex marking, a seriesof interconnected markings, or a single marking, provided somepositional and/or orientational information can be obtained.

If the system 10 cannot determine all of the degrees of freedom of theposition sensor 20, it may be necessary to place more than one positionsensor 20 near the location of interest in order to track the motion ofthe location of interest in all of the degrees of freedom. It is alsounderstood that in some situations, it will not be necessary to trackall of the possible positions and orientations of the location ofinterest. In these situations, the fact that a particular sensor element(not shown) of the position sensor 20 cannot track one degree offreedom, such as the roll, may not adversely affect use of the positionsensor 20 and may not require additional position sensors 20 to be used.

FIGS. 2C and 2D also illustrate use of the inflatable member 30. Inparticular, FIG. 2C shows the inflatable member 30 in the deflatedposition, and FIG. 2D shows the inflatable member 30 in the inflatedposition. It is understood that inflating the inflatable member 30 willfix the insertable portion 90 to a passageway or other part of theanatomical body.

In the preferred embodiment illustrated in FIGS. 2C and 2D, theapparatus 100 comprises an electromagnetic shield 45. Theelectromagnetic shield 45 may be a braided mesh, as is known in the art,to shield the electrical leads 26 from spurious electromagnetic signals.It is understood that the electromagnetic shield 45 is particularlypreferable in cases where the power level of the position signal S_(P)is not great, and therefore even minor spurious electromagnetic fieldscould adversely affect the position signal S_(p).

While the inflatable member 30 can be placed in manmade passageways,such as drilled holes into bones, the inflatable member 30 is also wellsuited for natural occurring passageways in the body, such as arteries,veins and airways. In smaller veins, particularly where the blood flowis not to a crucial part of the body, or alternate blood paths areavailable, the inflatable member 30 may encompass the entirecircumference of the insertable portion 90 as shown in FIGS. 2A, 2B, 2Cand 2D. In this case, inflating the inflatable member 30 may occlude thepassageway preventing fluid flow through the passageway.

In some cases, however, it is not desirable to completely occlude apassageway. This would be the case, for example, in an airway or mainartery. In these cases, it is preferable that the inflatable member 30comprises at least one lobe portion 3. In the preferred embodimentillustrated in FIG. 3A, the inflatable member 30 comprises three lobeportions 3 a, 3 b, 3 c and 3 d, located at 90 degrees with respect toeach other and around the insertable portion 90. FIG. 3A illustrates theinflatable member 30 in the inflated configuration, and thereby fixingthe insertable portion 90 to a part of the anatomical body, in this casethe passageway 300. It is understood that in the deflated configuration,the lobes 3 a, 3 b, 3 c and 3 d of the inflatable member 30 would benear the rigid portion 90 in order to permit insertion of the insertableportion 90 into the anatomical body.

It is apparent from FIG. 3A that by utilizing the lobe portions 3 a, 3b, 3 c, 3 d, fluid can still flow around the insertable portion 90 ofthe apparatus 100, which in this embodiment comprises the catheter 110,and therefore through the passageway 300. In this way, use of lobeportions 3 to fix the insertable portion 90 will not greatly adverselyaffect the fluid flow in a location of interest. This may beparticularly important depending on the pathology of the location ofinterest and the nature of the passageway 300.

FIG. 3A also shows in cross-section the sensor coil 21 located withinthe insertable portion 90. FIG. 3A also shows the guidewire path 40through which the guidewire 60 passes and the inflatable opening 44through which fluid can pass in order to inflate the inflatable member30, which in this case comprises the three lobes 3 a, 3 b, 3 c, 3 d,attached to a catheter 110 in this embodiment. It is understood that anapparatus 100 other than a catheter 110 could also be used with theinflatable member 30, such as an endoscope (not shown).

FIG. 3B shows a side view of the embodiment illustrated in FIG. 3A. AsFIG. 3B is a side view, only lobes 3 c and 3 a are illustrated. It isunderstood that lobes 3 d and 3 b would be entering out of and into thepage, respectively. FIG. 3B also shows the fiducial markings 70 atopposed ends of the insertable portion 90.

FIG. 3C shows a further embodiment of the present invention where thelobes, in this embodiment identified by reference numerals 3 x and 3 y,are barbed shaped. The barb shaped lobes 3 x and 3 y more rigidly securethe insertable portion 90 to the passageway 300. It is understood thatwhile two of the lobe portions 3 are barb shaped lobes 3 x, 3 y, theinsertable portion 90 may also have other lobes 3 which may not be barbshaped, but rather may be shaped similar to lobes 3 d and 3 b.

In a further preferred embodiment, the barbed shaped lobes 3 x, 3 y mayalso have a barbed end 33 for engaging the surface 301 of the passageway300. The barbed ends 33 may be made of more rigid material in order topermit engaging of the barb shaped lobes 3 x, 3 y to the surface 301 ofthe passageway 300. The barbed ends 33 would move towards the insertableportion 90 when the barb shaped lobes 3 x, 3 y are deflated.

FIGS. 4A and 4B illustrate a further embodiment of the presentinvention. As shown in FIG. 4A, the catheter 110 comprises a fixingmechanism 28 having a plurality 400 of longitudinally extending fingers410. The plurality 400 of longitudinally extending fingers 410 is fixedto the rigid portion 90 of the catheter 110 at point 430. Thelongitudinally extending fingers 410 also comprise a pivoting connection440, such as a hinge, permitting the longitudinally extending fingers410 to pivot about point 430.

Each longitudinally extending finger 410 has a gripping element 420 forgripping a surface 301 of the passageway 300 when the insertable portion90 is near the location of interest. As also illustrated in FIGS. 4A and4B, the insertable portion 90 has a bead 73 and band 74 as the fiducialmarkings 70. While the gripping element 420 is shown in FIGS. 4A and 4Bas being at the end of the longitudinally extending fingers 410, it isunderstood that the gripping element 420 could be at any location alongthe longitudinally extending fingers 410, such as at a bend (not shown)in a mid-portion.

FIG. 4B shows the longitudinally extending fingers 410 in the collapsedconfiguration where the gripping elements 420 are near the catheter 110.In the collapsed configuration, the insertable portion 90 of thecatheter 110 can be more easily inserted into the anatomical body. Oncethe insertable portion 90 is near the location of interest, thelongitudinally extending fingers 410 can be moved to the deployedconfiguration, shown in FIG. 4A, where the gripping elements 420 engagethe surface 301 of the passageway 300. The longitudinally extendingfingers 410 may be moved from the collapsed configuration to thedeployed configuration in any manner. For instance, the movement may beperformed by use of magnetic field acting on the finger 410. In apreferred embodiment, as illustrated in FIGS. 4A and 4B, the fingers 451are moved from the collapsed configuration to the deployed configurationby mechanically moving the supports 450 for each of the longitudinallyextending fingers 410. The supports 450 can be extended by signalsreceived in any manner, including mechanically, electrically,pneumatically, hydraulically or through the use of light signalstransmitted through fibre optics.

It is apparent from FIG. 4A that when the longitudinally extendingfingers 410 are in the deployed configuration, fluid can still flowaround the catheter 110, and therefore through the passageway 300. Inother words, deployment of the longitudinally extending fingers 410 doesnot occlude the passageway 300. Once the procedure is completed, thefingers 410 can be moved from the deployed configuration to thecollapsed configuration in the same manner in which they were deployed.

FIG. 5 shows an alternate embodiment where the fixing mechanism 28comprises barbs 200. The embodiment illustrated in FIG. 2E has threebarbs 201, 202, 203, but it is understood that even one barb 201 may besufficient. The barbs 200 form part of the insertable portion 90 thatholds the position sensor 20. In this embodiment, the barbs 200 form anintegral part of the insertable portion 90. Fiducial markings 70 areshown on barbs 201, 203, which are near opposed ends of the insertableportion 90.

Fixing mechanisms 28, such as the barbs 200, could be used inassociation with different parts of the anatomical body, and inparticular bone. For example, a manmade passageway, such as a drilledhole, could be made in a bone, such as a spine segment, the skull or thefemur. The insertable portion 90 could then be inserted into the drilledhole such that at least one of the barbs 200 fixes the insertableportion 90 to the bone. Depending on whether the procedure would need tobe repeated in the near future, and the size of the insertable portion90, it may be preferable to maintain the insertable portion 90 withinthe bone for an extended period of time.

In a further embodiment, illustrated in FIGS. 6A and 6B, the insertableportion 90 comprises a screw structure 610. The screw structure 610 isdesigned to screw the insertable portion 90 into a passageway within theanatomical body. Preferably, such a passageway would be made within boneso that the screw structure 610 can grip into the edges of thepassageway and draw the insertable portion 90 within the passageway torigidly fix it therein. As shown in FIG. 6A, the position sensor 20 iscontained within the insertable portion 90. FIG. 6B illustrates acannulated screwdriver 620 which can be used to rotate the insertableportion 90 so that the screw structure 610 can engage the edges of thepassageway to rigidly fix the insertable portion 90 therein. In thisembodiment, it is particularly preferable to have an insertable portion90 to withstand the torque forces encountered when the cannulatedscrewdriver 620 rotates the screw structure 610.

It is understood that the present invention also contemplates a methodfor registering a position sensor 20 to an anatomical body as describedabove. In particular, the present invention relates to a method offixing a position sensor 20 to an insertable portion 90 of a catheter110, the insertable portion 90 having fiducial markings 70 as describedabove. The method also comprises inserting the insertable portion 90 ofthe catheter 110 to the location of interest in the anatomical body. Thefiducial markings 70 are then detected on the insertable portion 90 ofthe catheter 110 to facilitate registration of the position sensor 20 inthe insertable portion 90 to the anatomical body.

As described above, it is understood that detecting the registrationstep includes detecting the fiducial markings 70 on the insertableportion 90. In the case where an imaging modality is used, the fiducialmarkings 70 would be detected on the insertable portion 90 by viewingthe image obtained through the image modality. It is understood thatother types of methods and means could be used to detect the fiducialmarkings 70 on the insertable portion 90 once the insertable portion 90has been inserted to the location of interest.

The position of the position sensor 20 in the frame of reference canthen be determined using the system 110. Having obtained a determinedposition of the position sensor 20 in the frame of reference using thesystem 10, the position sensor 20 can then be registered to theanatomical body by correlating the detected fiducial markings 70 to thedetermined position of the position sensor 20. In this way, the positionsensor 20 can be registered to the anatomical body and movement of theposition sensor 20 in the frame of reference can then be used to trackmovement of the location of interest in the anatomical body.

FIG. 7 shows a further embodiment of the present invention where theinsertable portion 90 comprises a stylette 790 which can be insertedinto a needle 702, as shown in FIGS. 8 a and 8 b. The stylette 790comprises a hollow stylette 700 as is known in the art. The hollowstylette 700 holds a position sensor 20 comprising a sensor coil 21, asdiscussed above. The sensor coil 21 is connected to sensor leads 26 fortransmitting the position signal S_(P) from the sensor coil 21 of theposition sensor 20 to the sensor interface unit 18 the control unit 12and the host computer 16, similar to the manner described above. Theposition signals S_(P) generated by the sensor coil 21 is indicative ofboth the position and orientation of the position sensor 20 held withinthe hollow stylette 700.

The stylette 790 also comprises fiducial markings 70. The fiducialmarkings 70 are detectable by an imaging modality when the stylette 790is inserted into the anatomical body. The fiducial markings 70 can beany markings that permit the position and orientation of the stylette790 to be determined from images obtained by imaging modality, asdiscussed above. In one preferred embodiment, as shown in FIG. 7, thefiducial markings comprise two bands 710, 712.

The stylette 790 also comprises a stylette hub 770. The stylette hub 770on the hollow stylette 700 mates with the corresponding needle hub 760on the needle 702. In this way the hollow stylette 700 can be releasablyfixed to the needle 702. This also ensures that the orientations of thehollow stylette 700 and the needle 702 are consistent.

This is the case in part, because the tip 701 of the stylette 790 is cutin a manor consistent with a tip 703 of the needle 702 and thereforethey are preferably oriented together.

Generally, a stylette is made of a wire (not shown) that simply blocksthe central cavity of needle 702. But because this stylette 790comprises a hollow stylette 700, a stylette plug 708 is preferably usedat the tip 703 of the needle 702 to prevent entry of tissue 690 into thehollow stylette 700.

FIG. 8 a shows the stylette 790 releasably fixed within the needle 702.As shown in FIG. 8 a, a sliding washer 750 is present on the needle 702,for contacting the tissue 690 of the anatomical body 190, as shown inFIG. 8 b. Accordingly, as shown in FIGS. 8 a and 8 b, the stylette hub770 is initially mated with the needle hub 760 to releasably fix theneedle 702 to the hollow stylette 700 and to ensure that theirorientations are consistent. The needle 702 can then be used to insertthe stylette 790 into the anatomical body 190. At this time, the slidingwasher 750 may be slid down the needle 702 to contact the tissue 690 ofthe anatomical body 190 as shown in FIG. 8 b.

At this time, an imaging modality may be used to detect the fiducialmarkings 70 on the stylette 790. In this way, the position sensor 20 canbe registered to the anatomical body 190 by correlating the fiducialmarkings 70 detected by the image modality to the determined position ofthe position sensor 20 in the frame of reference, as discussed above.

Accordingly, this is an additional embodiment of the present inventionwhere the apparatus 100 comprises a stylette 790 which can be insertedinto the anatomical body 190 using the needle 702. In this embodiment,the position sensor 20 can be used to ensure that the needle 702 hasbeen inserted into the location of interest in the anatomical body 190.At that time, the stylette 790 may be removed as shown in FIG. 8 c andthe needle 702 used to deliver a drug, therapeutic agent, or monitoractivity at the location of interest. A biopsy needle (not shown) couldalso be inserted through the needle 702 shown in FIG. 8 c so that thebiopsy needle protrudes from the tip of the needle 702 to take a biopsyfrom the tissue 690, such as parts of organs, tumours or body fluids.

It is understood that once the needle 702 is in the location of interestthe stylette 790 is no longer required for guidance and may be removedso that the needle 702 can be used in a procedure. However, if after theprocedure the needle 702 is required to be moved again, or the movementof the anatomical body 190 around the needle 702 is to be tracked, thestylette 790 may be reinserted into the needle 702 for a dynamic orpartial dynamic reference of the needle 702 in the anatomical body 190.It is understood that the stylette 790 may need to be reregistered if ithas been reinserted into the needle 702.

In a further embodiment, as shown in FIG. 10, the needle 702 may containon a surface 830 having therapy or sensor zones 820. The therapy orsensor zones 820 can likewise be inserted to a location of interest inthe anatomical body 190 using a position sensor 20 in the stylette 790.In FIG. 10, a stylette 790 has been shown removed from the needle 702,although this need not necessarily be done. Rather, the stylette 790 hasbeen shown removed in FIG. 10 for ease of illustration.

Once the needle 702 is in the location of interest or near the locationof interest, the therapy or sensor zones 820 can be activated. In otherwords, the therapy or sensor zones 820 can either provide a therapy tothe location of interest, or, sense activities in the location ofinterest. For instance, the therapy or sensor zones 820 located on thesurface 830 may be capable of measuring a second unrelated parametersuch as electrical activity, pressure, temperature, radiation or anyother type of parameter including content or concentration of othertypes of substances. The therapy or sensor zones 820 could also be usedto deliver a therapeutic substance. Such therapeutic substances caninclude energy in the form of heat, electrical signals, radio frequency(RF) energy, high frequency sound, ultrasound, microwave, x-rays,particle beams laser energy through a fibre optic cable, or other typesof radiation. The therapy or sensor zones 820 could also be used to scanthe inside of blood vessels or other anatomical features, such by usingmagnetic resonance. In a further embodiment, the therapy or sensor zones820 may facilitate delivering a therapy such as a drug or radioactiveseed that can be inserted into the needle 702 if the stylette 790 hasbeen removed.

As illustrated in FIG. 10, the stylette 790 comprises therapy/sensorleads 826 for transmitting the therapeutic signals S_(T) from thetherapy or sensor zones 820 indicative of the sensed second parameter asdiscussed above. The therapy/sensor leads 826 may also transmit controlsignals S_(C) to control the therapy/sensor zones 820.

It is understood that the stylette 790 preferably holds the positionsensor 20 within the needle 702 such that the position and orientationof the fiducial markings 70 with respect to the insertable portion 90remains substantially constant. It is understood that because the needle702 is generally more rigid than the hollow stylette 700, the rigidityof the needle 702 will assist in maintaining the position andorientation of the fiducial markings 70 with respect to stylette 790substantially constant.

FIG. 9 shows a further embodiment of the present invention comprising asecondary stylette 704 for holding secondary sensor 705. In thisembodiment, the secondary stylette 704 contains a secondary sensor 705and the secondary stylette leads 729 transmit the sensor signals S_(S)generated by the secondary sensor 705. Accordingly, in this embodiment,the apparatus 100 comprises a needle 702 and a hollow stylette 700releasably fixed within the needle 702, as well as the secondarystylette 704. The stylette 790 is initially releasably fixed within theneedle 702. Once the needle 702 has been inserted to or near a locationof interest, the stylette 790 can be removed and the secondary stylette704 inserted into the needle 702. The secondary sensor 705 of thesecondary stylette 704 can then sense a secondary parameter, likelyother than position, and transmit sensory signals S_(S) through thesecondary leads 729 to the sensor interface unit 18 or another interfaceunit (not shown).

FIG. 11 illustrates an embodiment where the position sensor 20 of thestylette 790 comprises a first position sensor 720 and a second positionsensor 722. The first position sensor 720 has a first sensor coil 721for generating a position signal S_(P1)indicative of the position of thefirst position sensor 720 in the fixed frame of reference. Likewise, thesecond position sensor 722 has a second sensor coil 723 for generating asecond position signal S_(P2) indicative of the position of the secondposition sensor 722 in the frame of reference. Preferably, the firstposition sensor 720 is longitudinally displaced from the second positionsensor 722. This is the case, in part, so that the first position sensor720 can be displaced from the second position sensor 722. Because thestylette 790 is designed to fit within the needle 702, the positionsensors 720, 722 can best be displaced by displacing them longitudinallyaxis of the stylette 790. Also, in a preferred embodiment, a secondarysensor or therapy device 820 is longitudinally located between the firstposition sensor 720 and the second position sensor 722. This permits theposition of the secondary sensor or therapy device 820 to be moreclearly determined, as it is located between the two position sensors720, 722.

Because the position sensors 720, 722 are displaced to such an extent,it is generally preferred that each of the position sensors 720, 722have their own fiducial markings 70 a and 70 b. The fiducial markings 70a, 70 b operate in a manner as described above, to facilitateregistration of the position sensors 720, 722 in the anatomical body 190by correlating the fiducial markings 70 a, 70 b detected by the imagingmodality to the determined position of the position sensors 720, 722irrespectively in the frame of reference. As discussed above, thestylette 790 may bend when the needle 702 has been removed. Because ofthis, it is generally necessary to have fiducial markings 70 a, 70 bassociated with each position sensor 720, 722, to accommodate for anybending by the stylette 790.

The position signals S_(P1), S_(P2) from the first and second positionsensors, 720, 722 travel along the sensor leads 826 to the sensorinterface unit 18, as discussed above. The stylette 790 illustrated inFIG. 11 also comprises leads 826. The leads 826 travel from thesecondary sensor or therapy device 820 to an interface unit, which mayalso be the sensor interface unit 18, for analysing the signals S_(T)from the secondary sensor or therapy device 820. Alternatively, thetherapy signals S_(T) may enter a separate interface device(not shown).In addition, control signals S_(C) may be sent to the secondary sensoror therapy device 820 to control its operation.

It may be desired to have the stylette 790 fixed to the anatomical body190 at or near a location of interest. This could be the case, forexample, if the position sensor 20 is to dynamically reference thetissue 690. In a preferred embodiment, the stylette 790 comprises afixing mechanism 28. The fixing mechanism 28 can comprise a simplemechanical element such as barbs 728 illustrated in FIG. 7. The barbs728 can be used, for example, to fix the stylette 790 in the tissue 690such as the liver or muscle.

In a further preferred embodiment, the fixing mechanism 28 comprisesdeployable stabilization members 828 as illustrated in FIG. 12. Thedeployable stabilization members 828 are preferably located near theposition sensor coil 21 to fix the position sensor 20 to the anatomicalbody 190 at or near a location of interest.

FIGS. 13 a, 13 b and 13 c illustrate operation of the deployablestabilization members 828. As illustrated in FIG. 13 a, when thestylette 790 is releasably fixed within the needle 702, the deployablestabilization members 828 are in a collapsed configuration. In FIG. 13b, the needle 702 is near or at the location of interest and thestylette hub 770 can be removed thereby releasing the needle 702 fromthe stylette 790 and permitting the needle 702 to slide out. Removingthe needle 702 causes the deployable stabilization members 828 to moveto a deployed configuration, as shown in FIG. 13 c. In the deployedconfiguration, the stylette 790 is releasably fixed to the anatomicalbody 190 near or at the location of interest. The position sensor 20 cannow sense the position of the location of interest. Once the procedureis completed, the stylette 790 can be removed by pulling the stylette790 from the anatomical body 190.

FIGS. 14 a, 14 b, 14 c and 14 d illustrate the registration procedureaccording to one preferred embodiment of the present invention. Asillustrated in FIG. 14 a, a reference coordinate system 900 is providedin the laboratory frame of reference. For ease of reference, thelaboratory reference coordinate system 900 will also correspond to thefield generator 14 coordinate system. As also illustrated in FIG. 14 a,there is an insertable portion 20 at position A and either anotherinsertable portion 20 or the same insertable portion 20 at a position B.As illustrated in FIG. 14 a, the insertable portions 20 at positions Aand B will have coordinates x₁, y₁ and z₁ and x₂, y₂ and z₂ in thereference coordinate system 900.

FIG. 14 b illustrates the coordinate measurements of points x₁, y₁, x₂and x₂, y₂ and Z₂ of positions A and B, respectively using the positionsensor 20. These would be the measurements made for instance by thefield generator 14. FIG. 14 b also illustrates the coordinate system ofthe imaging means or modality 901. As shown in FIG. 14 a, the positionsA and B are only determined in the coordinate system 900 of the fieldsensor 14 because the position sensor 90 can only be detected by thefield generator 14. In a preferred embodiment, the position sensor 20may also be able to determine the orientations along two axes shown aspitch and yaw in FIG. 14 b. More preferably, the position sensor 20 willalso be able to determine the orientation along the roll axis, althoughmost currently available position sensors cannot measure the orientationalong one axis, and generally the roll axis.

FIG. 14 c illustrates the images of the fiducial marking 70 asdetermined using the imaging modality. In this way, the coordinates atposition A and B are determined with respect to the coordinate system ofthe imaging means 901. It is also noticed that, in addition to the sixdegrees of position and orientation, the direction illustrated generallyby the arrow and reference numeral 991, is also determined. This isdetermined in the embodiment illustrated in FIG. 14 c in part becausethe fiducial markings 70 are asymmetrical fiducial markings 970 whichcan be differentiated in order to unambiguously determine the direction991 in the image coordinate system 901.

FIG. 14 d illustrates determination of the transformation matrix T bycorrelating the positions A, B as determined from the fiducial markings70 detected by the imaging modality in the coordinate system of theimaging means 901 to the position of the position sensors 20 and thecoordinate system of the field generator 900. In this way, thetransformation matrix T can be determined and used to correctly mapmeasurements of the movement of the position sensors 20 and theorientation of the position sensors 20 to images obtained through theimaging modality. Accordingly, once the transformation matrix T has beenobtained, the coordinate system of the field generator 900 has beenregistered to the coordinate system of the imaging means 901 permittingimage guided surgery to then take place.

As illustrated in FIGS. 14 c and 14 d, the position and orientation,illustrated by x, y, z and pitch, yaw, roll, may be determined in orderto facilitate determination of the transformation matrix T andregistration of the system. It is apparent that the direction 991determined from the fiducial markings 70 can also be of assistance toavoid any ambiguity. For instance, in cases where the fiducial markings70 are symmetrical about all of the axes, ambiguity can arise in theimaging modality, illustrated in FIG. 14 c, because it would not beeasily determinable which fiducial markings 70 is which. To overcomethis, in a preferred embodiment, as illustrated in FIGS. 14 c and 14 d,the fiducial markings 70 comprise asymmetrical fiducial markings 970which are asymmetrical about at least one axis of the insertable portion90.

FIGS. 15 a and 15 b also illustrate having asymmetrical fiducialmarkings 971, 972 which are asymmetrical about at least one axis, thisbeing the y axis as illustrated in FIGS. 15 a and 15 b. The asymmetricalfiducial markings 970 facilitate unambiguous registration by assistingin determining the direction 991 of the sensor 20.

This is further illustrated in FIGS. 16 a and 16 b which illustrate theimage which would be obtained of the fiducial markings 971, 972 usingthe image modality. As illustrated in FIGS. 16 a, 16 b, the asymmetricalfiducial markings are asymmetrical about at least the y axis. Thisfacilitates determination of the direction 991. Had the fiducialmarkings been symmetrical about the y axis (not shown), the direction991 could not be unambiguously determined. It is also apparent that thefiducial markings 971, 972 are symmetrical about the x-axis. In thisway, orientation along the x-axis cannot be easily determined. However,as indicated above, many position sensors 20 cannot determineorientation along one axis, such as the roll axis. In this case,preferably the x-axis, about which the fiducial markings 971, 972 aresymmetrical, coincide with the x-axis about which the markings 971, 972are symmetrical so that lack of determination of orientation along thisaxis is not significant.

FIGS. 17 a, 17 b and 17 c illustrate further preferred embodiments ofthe present invention where the rigid portion 990 comprises a mantle999. The mantle 999 is manufactured of a material which can be imaged inthe imaging modality. The mantle 999 may constitute the rigid portion990 or alternatively may be contained within an outer portion 981 or maybe encased or contained within material not imaged in the imagingmaterial. The mantle 999 may be a continuum having a continuous 2 or 3dimensional shape, or, may be two or more discrete shapes. In this way,the mantle 999 may be considered as comprising fiducial markings 70along the entire surface. The mantle 999 is rigidly attached by therigid attachment 921 to the position sensor 920. The mantle 999 is shownas being asymmetric about at least one axis, in this case the y axis, asalso illustrated in the profile shown in FIG. 17 a. In this way, thedirection 991 of the mantle 999, as well as the direction of the sensor920 may be unambiguously determined. mantlemantle

By way of contrast, FIGS. 18 a, 18 b and 18 c illustrate a furtherembodiment of a mantle 1000 rigidly attached to a sensor 920. The mantle1000 shown in FIGS. 18 a and 18 c can also be imaged by an imagingmodality. However, the mantle 1000 is actually symmetric along all threeaxes as illustrated in FIGS. 18 a, 18 b and 18 c and in this case, it isnot possible to unambiguously determine the direction using mantle 991.

FIGS. 19 a and 19 b show a further embodiment of the present inventionhaving a mantle 1001 which is completely asymmetric. In other words, themantle 1001 is asymmetric along all three axes. This further facilitatesunambiguous registration of the sensor 920 because the direction 991 canbe unambiguously determined similar to the mantle 999. Furthermore,because the mantle 1001 is completely asymmetrical, and has no plane ofreflective symmetry, the mantle 1001 can be used to determine theposition of the insertable portion to facilitate unambiguousregistration. Because the mantle 1001 has completely asymmetrical shape,it is well suited to be used with position sensors 20 which measureposition and orientation in six degrees of freedom, namely x, y, z andpitch, yaw and roll. Accordingly, having fiducial markings on a mantlewhich comprises as a whole fiducial markings that is axiallyasymmetrical on at least one axis, facilitates unambiguous registrationby assisting in determining the position (x,y,z) and orientation, (yaw,pitch, roll) and direction 991 of the position sensor 920 in the imagingmodality.

It is understood that the present device can be used in any anatomicalbody. For instance, the device 100 can be used on a living human body,as well as a cadaver, such as during an autopsy. Furthermore, the device100 may be used in non-human anatomical bodies, such as in veterinaryuse on animals.

It is also understood that the position sensor 20 may be inserted forany reason. For example, the position sensor 20 may be inserted toassist in treatment, diagnosis or monitoring. This is illustrated, forexample, at least in FIG. 11 discussed above.

While the present invention has been described in terms of a positionsensor 20 comprising a particular type of sensor element, namely themagnetic sensor coil 21, it is understood that the present invention isnot limited to this type of sensor. Rather, any type of position sensor,which can sense movement in at least some degrees of freedom, can beused. In particular, fibre optic position sensors, which sense changesin light, could also be used. Furthermore, while the present inventionhas been described in terms of a magnetic sensor coil 21 connected toelectrical leads 26, it is understood that the electrical leads 26 maynot be required. For instance, if a fibre optic position sensor 20 isutilized, electrical leads 26 may be replaced by fibre optic cables (notshown). In this case, the electromagnetic shielding 45 may not beneeded. It is further understood that the present invention is notlimited to position sensors 20 which require an electrical lead 26 orfibre optic (not shown) to transmit the position signals S_(P)indicative of the movement of the position sensor 20. Rather, theposition signals S_(P) may be transmitted wirelessly directly from theposition sensor 20 to a position sensor receiver (not shown) in theframe of reference.

It is also understood that reference has been made to placing theinsertable portion 90 near the location of interest and at the locationof interest. It is understood that, in this context, near the locationof interest also includes at the location of interest, and, how near theposition sensor 20 can be placed to the location of interest wouldchange with each situation and depend on the pathology and part of theanatomical body 190 which is in the location of interest. For instance,if a location of interest comprising an organ such as the kidney,position sensor 20 may easily be placed at the location of interest bybeing placed within passageways 300, such as veins, within the kidney.Conversely, if the location of interest comprises the spinal cord, thespinal cord may be tracked by placing position sensors in spine segmentsnear the spinal cord. Accordingly, it is understood that both “near thelocation of interest” and “at the location of interest” refer to placingthe insertable portion 90 in a location which can best track thelocation of interest in the anatomical body 190 for the procedure beingperformed.

It is understood that the insertable portion 90 is rigid to the extentrequired to keep the position sensor 20 in a known position andorientation with respect to the fiducial markings 70 during theregistration procedure. In other words, if the position sensor 20 can beflexible, so that it can be bent and still operate, then the insertableportion 90 can be more flexible. Accordingly, the insertable portion 90is as rigid as necessary for the position sensor 20 to operate.Furthermore, it is contemplated that the insertable portion 90 could berigid for a predetermined period of time, such as during registration,and could be more flexible at other times, such as by removing aremovable rigid member (not shown) temporarily forming parts of theinsertable portion 90.

It is also understood that while the invention has disclosed a number ofdifferent fixing mechanisms 28 for fixing the insertable portion 90containing a position sensor 20, the fixing mechanisms 28 are notlimited to this embodiment. Rather, the fixing mechanisms 28 could beused whether or not the catheter 110 contains a position sensor 20, andregardless of the use of the catheter 110.

It will be understood that, although various features of the inventionhave been described with respect to one or another of the embodiments ofthe invention, the various features and embodiments of the invention maybe combined or used in conjunction with other features and embodimentsof the invention as described and illustrated herein.

Although this disclosure has described and illustrated certain preferredembodiments of the invention, it is to be understood that the inventionis not restricted to these particular embodiments. Rather, the inventionincludes all embodiments that are functional, electrical or mechanicalequivalents of the specific embodiments and features that have beendescribed and illustrated herein.

1. An apparatus insertable into an anatomical body, said apparatuscomprising: an insertable portion for holding a position sensor that cantransmit a signal indicative of its position in a frame of reference;fiducial markings on the insertable portion, said fiducial markingsbeing detectable by an imaging modality when the insertable portion isinserted in the anatomical body and permitting the position andorientation of the insertable portion to be determined, said insertableportion substantially rigidly holding the position sensor at a knownspatial position with respect to the fiducial markings; wherein thefiducial markings are non-symmetrical about at least a first axis of theinsertable portion; wherein, after insertion in the anatomical body, thefiducial markings can be detected by the imaging modality to facilitateunambiguous registration to the anatomical body of the position sensorrigidly held in the insertable portion by correlating the fiducialmarkings detected by the imaging modality to the determined position ofthe position sensor in the frame of reference.
 2. The apparatus asdefined in claim 1 further comprising: a fixing mechanism for fixing theinsertable portion to the anatomical body; wherein, when the insertableportion is inserted into the anatomical body to a location of interest,the fixing mechanism rigidly fixes the insertable portion to a part ofthe anatomical body near the location of interest; and wherein thefiducial markings can be detected while the insertable portion is fixedto the part of the anatomical body near the location of interest.
 3. Theapparatus as defined in claim 2 further comprising a catheter forinserting the insertable portion into the anatomical body; wherein thefixing mechanism comprises an inflatable member which inflates when theinsertable portion is at the location of interest to releasably fix theinsertable portion of the catheter to the part of the anatomical bodynear the location of interest.
 4. The apparatus as defined in claim 3wherein the part of the anatomical body is a passageway near thelocation of interest; and wherein the inflatable member comprises atleast one lobe portion, and, wherein, when the at least one lobe portionof the inflatable member is inflated to fix the insertable portion tothe part of the anatomical body, fluid can flow around the catheter andthrough the passageway.
 5. The apparatus as defined in claim 4 whereinthe at least one lobe portion has a barbed end for engaging a surface ofthe passageway.
 6. The apparatus as defined in claim 2 furthercomprising a catheter for inserting the insertable portion into theanatomical body; and wherein the fixing mechanism comprises a pluralityof longitudinally extending fingers affixed to the insertable portion,each finger having a gripping element for gripping a surface of apassageway near the location of interest, said fixing mechanism having acollapsed configuration where the gripping element is near the catheter,and a deployed configuration where at least one gripping element gripsthe surface of the passageway; and wherein when the fingers are in thedeployed configuration, fluid can flow around the catheter and throughthe passageway.
 7. The apparatus as defined in claim 2 wherein thefixing mechanism is selected from the group consisting of a screw forsecuring the insertable portion to the anatomical body at the locationof interest; andat least one barb for rigidly fixing the insertableportion of the catheter to the anatomical body at the location ofinterest.
 8. The apparatus as defined in claim 1 wherein the imagingmodality that can detect the fiducial markings is selected from thegroup consisting of CT scans, fluoroscopic images and ultrasound images.9. The apparatus as defined in claim 1 wherein the fiducial markingscomprise at least two markings said at least two markings beingasymmetrically placed on the insertable portion that permit the positionand orientation of the insertable portion to be determined.
 10. Theapparatus as defined in claim 1 wherein the fiducial markings are notsymmetrical about at least the first axis and a second axis of theinsertable portion.
 11. The apparatus as defined in claim 1 wherein thefiducial markings comprise a mantle which is detectable by the imagingmodality and has a shape that is asymmetrical along at least one axis.12. The apparatus as defined in claim 11 wherein the shape of the mantleis asymmetrical along three axes.
 13. The apparatus as defined in claim11 wherein the mantle is rigidly attached to the position sensor. 14.The apparatus as defined in claim 11 wherein the signal transmitted bythe position sensor is indicative of its position and orientation exceptfor a roll axis and wherein the shape of the mantle is asymmetricalexcept for a symmetric axis; and wherein the symmetric axis mantleiscoincident with the roll axis.
 15. The apparatus as defined in claim 11wherein the signal transmitted by the position sensor is indicative ofits position and orientation in six degrees of freedom; and wherein theshape of the mantle is completely asymmetrical.
 16. The apparatus asdefined in claim 1 further comprising a needle for inserting theinsertable portion into the anatomical body, said insertable portionbeing releasably fixed within the needle.
 17. The apparatus as definedin claim 16 further comprising a sensory stylette holding a sensor; andwherein the insertable portion can be removed from the needle and thesensory stylette inserted while the needle is inserted in the anatomicalbody.
 18. The apparatus as defined in claim 16 wherein the insertableportion holds a first position sensor and a second position sensorlongitudinally displaced from the first position sensor.
 19. Theapparatus as defined in claim 18 further comprising: at least one zoneon a surface of the needle, said at least one zone being longitudinallylocated between the first position sensor and the second positionsensor.
 20. The apparatus as defined in claim 16 wherein the fiducialmarkings comprise at least two markings displaced longitudinally alongthe insertable portion which permit the position and orientation of theinsertable portion to be determined from images obtained by the imagingmodality.
 21. A method of registering a position sensor to an anatomicalbody, said method comprising the steps of: (a) fixing a position sensorto an insertable portion of an apparatus, said insertable portion havingfiducial markings thereon; (b) inserting the insertable portion of theapparatus to a location of interest in the anatomical body; and (c)detecting the non-symmetrical fiducial markings on the insertableportion of the apparatus to facilitate registration of the positionsensor in the insertable portion to the anatomical body by: (c1)detecting the fiducial markings on the insertable portion; (c2)determining the position of the position sensor in a frame of reference;and (c3) registering the position sensor to the anatomical body bycorrelating the detected fiducial markings to the determined position ofthe position sensor in the frame of reference.
 22. The method as definedin claim 21 further comprising: (i) detecting the non-symmetricalfiducial marking to determine a position, orientation and direction ofthe insertable portion in image space; (ii) determining the position andorientation of the position sensor along at least two axes in the frameof reference; and (iii) registering the position sensor to theanatomical body by correlating the determined position, orientation anddirection of the insertable portion from the detected non-symmetricalfiducial markings to the determined position and orientation of theposition sensor in the frame of reference.
 23. A device for facilitatingtracking of an apparatus in an anatomical body, said device comprising:an insertable portion for holding a position sensor that can transmit aposition signal indicative of its position in a frame of reference;non-symmetrical fiducial markings on the insertable portion, saidnon-symmetrical fiducial markings being detectable by an imagingmodality to facilitate unambiguous registration of the position sensorheld in the insertable portion to the anatomical body; wherein theapparatus can insert the insertable portion into the anatomical body,and, the position signal transmitted from the position sensor indicatesthe position of the apparatus near the position sensor; wherein theinsertable portion substantially rigidly holds the sensor at a knownspatial position with respect to the fiducial markings; and wherein,after insertion of the insertable portion in the anatomical body, animage of the insertable portion can be obtained by the imaging modality,and, the position sensor can be registered to the anatomical body bycorrelating the fiducial markings detected by the imaging modality tothe determined position of the position sensor in the frame ofreference.
 24. The device as defined in claim 23 wherein the insertableportion further comprises: (i) a stylette hub which mates with a needlehub associated with the needle for orienting the hollow stylette withthe needle; and (ii) a stylette plug for preventing entry of tissue intothe hollow stylette during insertion into the anatomical body.
 25. Thedevice as defined in claim 24 wherein mating the needle hub with thestylette hub releasably fixes the hollow stylette to the needle.
 26. Thedevice as defined in claim 23 wherein the apparatus comprises a catheterand the insertable portion is rigidly fixed to the catheter.